This type of technique is described in Patent Document 1 for example. In a sound absorbing structure described in Patent Document 1, a fiber material and a porous plate are provided so as to overlie each other, and an air layer is provided behind the porous plate or the fiber material. Density ρ (kg/m3) of the fiber material and thickness t (mm) of the fiber material preferably satisfy the relationship of ρ×t≧0.01 kg/m2.